Lung Cancer


“What is your stage?” is a question you may often be asked when sharing your lung cancer diagnosis with loved ones and friends. The stage is important to know because it describes the extent of cancer within your body and how far it may have progressed from where it began. Your doctor uses this valuable information to select the most effective treatment option for you.

To assign a stage, your doctor will evaluate the results of laboratory tests of your blood, urine, body fluids and tissues to look for biomarkers. The doctor also reviews the results of scans including a chest CT, PET or brain MRI. Your doctor may order a biopsy so a pathologist can look at the cells under a microscope to determine whether the growth is cancerous and, if so, its stage of development. A pathologist is a doctor with specialized training in identifying diseases by studying cells and tissues under a microscope. Your pathology report will describe the results of tissue sample testing and may include results from biomarker testing, tumor molecular analysis or other tests. Ask your doctor to discuss the pathology report with you and to explain how these findings will affect your treatment options. You can also request a copy of the report for your records.

Some biopsies are performed with a needle, although certain situations require that a piece or all of the tumor be removed surgically to determine a diagnosis. Your doctor will also consider the results of your physical exams, diagnostic tests and imaging studies. Computed tomography (CT) of the chest and magnetic resonance imaging (MRI) of the brain are routine.

With today’s emphasis on personalizing cancer care, including targeting a tumor’s genetic or molecular abnormalities, pathology report results are becoming increasingly important in the diagnosis and treatment of lung cancer. New drug therapies continue to become available for targeting specific mutations, yet these therapies can only be used if they are confirmed with molecular testing.

The TNM (tumor, node, metastasis) system, developed by the American Joint Committee on Cancer (AJCC) and the International Association for the Study of Lung Cancer, is used to classify and stage lung cancer (see Table 1).

The T category specifies the primary tumor’s size and location. The N category indicates whether lymph nodes show evidence of cancer cells. If so, the location of these lymph nodes is important because it shows how far the disease has progressed. The M category describes distant metastasis (spread), if any. Cancer can spread by growing into nearby tissue, traveling through lymph vessels or blood vessels to other parts of the body. An M subcategory may be added based on the presence of tumor cells that can be detected only by using a microscope or molecular testing. For illustration purposes, the tumors in Figure 1 are shown on one side of the lungs. They may, however, be present in any area of the lungs. Ask your doctor about your diagnosis.

Non-small cell lung cancers (NSCLC) may be staged as Stage 0 through Stage IV (see Table 2). Stage 0 is also known as in situ, and it is a precursor of an invasive cancer. Stages I and II are generally confined to the local area where the cancer is found with or without adjacent lymph node involvement. They are treated as early stage and are considered potentially curable; therefore, every effort should be made to render a cure for these diagnoses. Stage III NSCLC is considered locally advanced, still confined to the chest but has spread to regional lymph nodes outside the lung in the mediastinum. Stage IV is locally or regionally advanced disease that has spread to distant sites, such as the brain, liver or bone.

Commonly, doctors also use the AJCC TNM classification to stage small cell lung cancer (SCLC). Some of the tests and procedures performed to diagnose SCLC are also used to stage it. Those commonly include MRI, CT, positron emission tomography (PET) and a bone scan.

As an additional tool to guide treatment, doctors may describe SCLC as limited stage (corresponding to Stages I to III) or extensive-stage (corresponding to Stage IV).
  • Limited-stage SCLC is confined to one part of the chest, in just one part of the lung and in nearby lymph nodes.
  • Extensive-stage SCLC has spread to other parts of the body, such as the area between the lungs, bone, brain or other lung.

Table 1. Stages of Lung Cancer

Stage TNM classifications
Occult carcinoma TX, N0, M0
0 Tis, N0, M0
IA1 T1mi, N0, M0
T1a, N0, M0
IA2 T1b, N0, M0
IA3 T1c, N0, M0
IB T2a, N0, M0
T2b, N0, M0
T1a or T1b or T1c, N1, M0
T2a or T2b, N1, M0
T3, N0, M0
T1a or T1b or T1c, N2, M0
T2a or T2b, N2, M0
T3, N1, M0
T4, N0 or N1, M0
T1a or T1b or T1c, N3, M0
T2a or T2b, N3, M0
T3, N2, M0
T4, N2, M0
T3, N3, M0
T4, N3, M0
Any T, Any N, M1
Any T, Any N, M1a or M1b
Any T, Any N, M1c

Table 2. AJCC system for classifying lung cancer

Category Definition
Tumor (T)
TX Primary tumor cannot be assessed, or tumor proven by the presence of malignant (cancerous) cells in sputum (mucus that has been coughed up) or bronchial washings (cells collected from inside the airways) but not visualized by imaging or bronchoscopy.
T0 No evidence of primary tumor.
Tis Carcinoma in situ.
Squamous cell carcinoma in situ (SCIS).
Adenocarcinoma in situ (AIS): adenocarcinoma with pure lepidic pattern (on the alveolar lining), ≯ (not more than) 3cm in greatest dimension.
Tumor ≯ (not more than) 3 cm in greatest dimension, surrounded by lung or visceral pleura (membrane surrounding the lung), without bronchoscopic evidence of invasion more proximal than the lobar bronchus (i.e., not in the main bronchus).
Minimally invasive adenocarcinoma: adenocarcinoma (≯ [not more than] 3 cm in greatest dimension) with a predominantly lepidic pattern (on the alveolar lining) and ≯ (not more than) 5 mm invasion in greatest dimension.
Tumor ≯ (not more than) 1 cm in greatest dimension.
Tumor > (more than) 1 cm but ≯ (not more than) 2 cm in greatest dimension.
Tumor > (more than) 2 cm but ≯ (not more than) 3 cm in greatest dimension.
Tumor > (more than) 3 cm but ≯ (not more than) 5 cm or having any of the following features:
    • Involves the main bronchus regardless of distance to the carina (ridge at the base
      of the trachea), but without involvement of the carina.
    • Invades visceral pleura (membrane surrounding the lung).
    • Associated with atelectasis (collapse of part of the lung) or obstructive pneumonitis
      (inflammation of lung tissues) that extends to the hilar region, involving part or all
      of the lung.
Tumor > (more than) 3 cm but ≯ (not more than) 4 cm in greatest dimension.
Tumor > (more than) 4 cm but ≯ (not more than) 5 cm in greatest dimension.
T3 Tumor > (more than) 5 cm but ≯ (not more than) 7 cm in greatest dimension or directly invading any of the following: parietal pleura (outer lung membrane), chest wall (including superior sulcus tumors), phrenic nerve (nerve that helps control breathing), parietal pericardium; or separate tumor nodule(s) in the same lobe as the primary.
T4 Tumor > (more than) 7 cm or tumor of any size invading one or more of the following: diaphragm, mediastinum (area between the lungs), heart, great vessels, trachea (windpipe), recurrent laryngeal nerve (nerve that helps speech), esophagus, vertebral body, or carina (at base of the trachea); separate tumor nodule(s) in an ipsilateral lobe (lobe that is on the same side of the body) different from that of the primary.
Node (N)
NX Regional lymph nodes cannot be assessed.
N0 No regional lymph node metastasis.
N1 Metastasis in ipsilateral (on the same side) peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes, including involvement by direct extension.
N2 Metastasis in ipsilateral (on the same side) mediastinal and/or subcarinal lymph node(s).
N3 Metastasis in contralateral (on the opposite side) mediastinal, contralateral hilar, ipsilateral (on the same side) or contralateral scalene, or supraclavicular lymph node(s) (located above the collarbone).
Metastasis (M)
M0 No distant metastasis.
Distant metastasis.
Separate tumor nodule(s) in a contralateral (on the opposite side) lobe; tumor with pleural or pericardial nodules or malignant pleural or pericardial effusion.
Single extrathoracic (outside of the lung) metastasis in a single organ (including involvement of a single nonregional node).
Multiple extrathoracic (outside of the lung) metastases in a single organ or in multiple organs.

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.